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Physiological Reviews Jan 2023Taste and smell play a key role in our ability to perceive foods. Overconsumption of highly palatable energy-dense foods can lead to increased caloric intake and... (Review)
Review
Taste and smell play a key role in our ability to perceive foods. Overconsumption of highly palatable energy-dense foods can lead to increased caloric intake and obesity. Thus there is growing interest in the study of the biological mediators of fat taste and associated olfaction as potential targets for pharmacologic and nutritional interventions in the context of obesity and health. The number of studies examining mechanisms underlying fat taste and smell has grown rapidly in the last 5 years. Therefore, the purpose of this systematic review is to summarize emerging evidence examining the biological mechanisms of fat taste and smell. A literature search was conducted of studies published in English between 2014 and 2021 in adult humans and animal models. Database searches were conducted using PubMed, EMBASE, Scopus, and Web of Science for key terms including fat/lipid, taste, and olfaction. Initially, 4,062 articles were identified through database searches, and a total of 84 relevant articles met inclusion and exclusion criteria and are included in this review. Existing literature suggests that there are several proteins integral to fat chemosensation, including cluster of differentiation 36 (CD36) and G protein-coupled receptor 120 (GPR120). This systematic review will discuss these proteins and the signal transduction pathways involved in fat detection. We also review neural circuits, key brain regions, ingestive cues, postingestive signals, and genetic polymorphism that play a role in fat perception and consumption. Finally, we discuss the role of fat taste and smell in the context of eating behavior and obesity.
Topics: Animals; Humans; Feeding Behavior; Obesity; Smell; Taste; Taste Buds
PubMed: 36409650
DOI: 10.1152/physrev.00061.2021 -
Ageing Research Reviews Sep 2021Alterations in olfactory functions are proposed to be early biomarkers for neurodegeneration. Many neurodegenerative diseases are age-related, including two of the most... (Review)
Review
Alterations in olfactory functions are proposed to be early biomarkers for neurodegeneration. Many neurodegenerative diseases are age-related, including two of the most common, Parkinson's disease (PD) and Alzheimer's disease (AD). The establishment of biomarkers that promote early risk identification is critical for the implementation of early treatment to postpone or avert pathological development. Olfactory dysfunction (OD) is seen in 90% of early-stage PD patients and 85% of patients with early-stage AD, which makes it an attractive biomarker for early diagnosis of these diseases. Here, we systematically review widely applied smelling tests available for humans as well as olfaction assessments performed in some animal models and the relationships between OD and normal aging, PD, AD, and other conditions. The utility of OD as a biomarker for neurodegenerative disease diagnosis and future research directions are also discussed.
Topics: Aging; Alzheimer Disease; Animals; Humans; Neurodegenerative Diseases; Olfaction Disorders; Parkinson Disease; Smell
PubMed: 34325072
DOI: 10.1016/j.arr.2021.101416 -
The Cochrane Database of Systematic... Nov 2022Perception is the ability to understand information from our senses. It allows us to experience and meaningfully interact with our environment. A stroke may impair... (Review)
Review
BACKGROUND
Perception is the ability to understand information from our senses. It allows us to experience and meaningfully interact with our environment. A stroke may impair perception in up to 70% of stroke survivors, leading to distress, increased dependence on others, and poorer quality of life. Interventions to address perceptual disorders may include assessment and screening, rehabilitation, non-invasive brain stimulation, pharmacological and surgical approaches.
OBJECTIVES
To assess the effectiveness of interventions aimed at perceptual disorders after stroke compared to no intervention or control (placebo, standard care, attention control), on measures of performance in activities of daily living. SEARCH METHODS: We searched the trials registers of the Cochrane Stroke Group, CENTRAL, MEDLINE, Embase, and three other databases to August 2021. We also searched trials and research registers, reference lists of studies, handsearched journals, and contacted authors.
SELECTION CRITERIA
We included randomised controlled trials (RCTs) of adult stroke survivors with perceptual disorders. We defined perception as the specific mental functions of recognising and interpreting sensory stimuli and included hearing, taste, touch, smell, somatosensation, and vision. Our definition of perception excluded visual field deficits, neglect/inattention, and pain.
DATA COLLECTION AND ANALYSIS
One review author assessed titles, with two review authors independently screening abstracts and full-text articles for eligibility. One review author extracted, appraised, and entered data, which were checked by a second author. We assessed risk of bias (ROB) using the ROB-1 tool, and quality of evidence using GRADE. A stakeholder group, comprising stroke survivors, carers, and healthcare professionals, was involved in this review update.
MAIN RESULTS
We identified 18 eligible RCTs involving 541 participants. The trials addressed touch (three trials, 70 participants), somatosensory (seven trials, 196 participants) and visual perception disorders (seven trials, 225 participants), with one (50 participants) exploring mixed touch-somatosensory disorders. None addressed stroke-related hearing, taste, or smell perception disorders. All but one examined the effectiveness of rehabilitation interventions; the exception evaluated non-invasive brain stimulation. For our main comparison of active intervention versus no treatment or control, one trial reported our primary outcome of performance in activities of daily living (ADL): Somatosensory disorders: one trial (24 participants) compared an intervention with a control intervention and reported an ADL measure. Touch perception disorder: no trials measuring ADL compared an intervention with no treatment or with a control intervention. Visual perception disorders: no trials measuring ADL compared an intervention with no treatment or control. In addition, six trials reported ADL outcomes in a comparison of active intervention versus active intervention, relating to somatosensation (three trials), touch (one trial) and vision (two trials). AUTHORS' CONCLUSIONS: Following a detailed, systematic search, we identified limited RCT evidence of the effectiveness of interventions for perceptual disorders following stroke. There is insufficient evidence to support or refute the suggestion that perceptual interventions are effective. More high-quality trials of interventions for perceptual disorders in stroke are needed. They should recruit sufficient participant numbers, include a 'usual care' comparison, and measure longer-term functional outcomes, at time points beyond the initial intervention period. People with impaired perception following a stroke should continue to receive neurorehabilitation according to clinical guidelines.
Topics: Adult; Humans; Activities of Daily Living; Perceptual Disorders; Stroke; Stroke Rehabilitation; Vision Disorders; Randomized Controlled Trials as Topic
PubMed: 36326118
DOI: 10.1002/14651858.CD007039.pub3 -
European Eating Disorders Review : the... Sep 2022The aim of this study was to assess the relationship between sensory processing and a broad range of eating behaviours across the lifespan. (Review)
Review
OBJECTIVES
The aim of this study was to assess the relationship between sensory processing and a broad range of eating behaviours across the lifespan.
METHODS
Five electronic databases of published and unpublished quantitative studies were systematically searched, evaluated for risk of bias and synthesised according to identified eating outcomes.
RESULTS
Across 25 studies, there was consistent evidence of a relationship between sensory processing and a range of eating behaviours. There was early evidence for the particular role of taste/smell sensitivities, as well as hypersensitivities, although future research is needed looking at different sensory patterns and modalities. There was also tentative evidence to suggest this relationship extends across development.
DISCUSSION
Study findings are discussed in relation to implications for sensory-based eating and feeding interventions and the development of eating disorders. Methodological and conceptual limitations are discussed and suggestions for future research are made to address these limitations. A broader investigation of multi-sensory issues and clearly defined eating behaviours, including disordered eating in clinically diagnosed samples, will allow for a more comprehensive and robust understanding of the relationship between sensory processing and eating behaviours in autism.
Topics: Autistic Disorder; Feeding Behavior; Feeding and Eating Disorders; Humans; Perception; Taste
PubMed: 35737818
DOI: 10.1002/erv.2920 -
Neuropsychology Review Mar 2024Olfactory training (OT), or smell training,consists of repeated exposure to odorants over time with the intended neuroplastic effect of improving or remediating... (Review)
Review
Olfactory training (OT), or smell training,consists of repeated exposure to odorants over time with the intended neuroplastic effect of improving or remediating olfactory functioning. Declines in olfaction parallel declines in cognition in various pathological conditions and aging. Research suggests a dynamic neural connection exists between olfaction and cognition. Thus, if OT can improve olfaction, could OT also improve cognition and support brain function? To answer this question, we conducted a systematic review of the literature to determine whether there is evidence that OT translates to improved cognition or altered brain morphology and connectivity that supports cognition. Across three databases (MEDLINE, Scopus, & Embase), 18 articles were identified in this systematic review. Overall, the reviewed studies provided emerging evidence that OT is associated with improved global cognition, and in particular, verbal fluency and verbal learning/memory. OT is also associated with increases in the volume/size of olfactory-related brain regions, including the olfactory bulb and hippocampus, and altered functional connectivity. Interestingly, these positive effects were not limited to patients with smell loss (i.e., hyposmia & anosmia) but normosmic (i.e., normal ability to smell) participants benefitted as well. Implications for practice and research are provided.
Topics: Humans; Brain; Cognition; Olfaction Disorders; Olfactory Training; Smell
PubMed: 36725781
DOI: 10.1007/s11065-022-09573-0 -
The Cochrane Database of Systematic... Mar 2021This living systematic review is one of several Cochrane Reviews evaluating the medical management of patients with chronic rhinosinusitis. Chronic rhinosinusitis is... (Meta-Analysis)
Meta-Analysis
BACKGROUND
This living systematic review is one of several Cochrane Reviews evaluating the medical management of patients with chronic rhinosinusitis. Chronic rhinosinusitis is common. It is characterised by inflammation of the nasal and sinus linings, nasal blockage, rhinorrhoea, facial pressure/pain and loss of sense of smell. It occurs with or without nasal polyps. 'Biologics' are medicinal products produced by a biological process. Monoclonal antibodies are one type, already evaluated in other inflammatory conditions (e.g. asthma and atopic dermatitis).
OBJECTIVES
To assess the effects of biologics for the treatment of chronic rhinosinusitis.
SEARCH METHODS
The Cochrane ENT Information Specialist searched the Cochrane ENT Register; CENTRAL (2020, Issue 9); Ovid MEDLINE; Ovid Embase; Web of Science; ClinicalTrials.gov; ICTRP and additional sources for published and unpublished studies. The date of the search was 28 September 2020.
SELECTION CRITERIA
Randomised controlled trials (RCTs) with at least three months follow-up comparing biologics (monoclonal antibodies) against placebo/no treatment in patients with chronic rhinosinusitis.
DATA COLLECTION AND ANALYSIS
We used standard Cochrane methodological procedures. Our primary outcomes were disease-specific health-related quality of life (HRQL), disease severity and serious adverse events (SAEs). The secondary outcomes were avoidance of surgery, extent of disease (measured by endoscopic or computerised tomography (CT) score), generic HRQL and adverse effects (nasopharyngitis, including sore throat). We used GRADE to assess the certainty of the evidence for each outcome.
MAIN RESULTS
We included 10 studies. Of 1262 adult participants, 1260 had severe chronic rhinosinusitis with nasal polyps; 43% to 100% of participants also had asthma. Three biologics, with different targets, were evaluated: dupilumab, mepolizumab and omalizumab. All of the studies were sponsored or supported by industry. For this update (2021) we have included two new studies, including 265 participants, which reported data relating to omalizumab. Anti-IL-4Rα mAb (dupilumab) versus placebo/no treatment (all receiving intranasal steroids) Three studies (784 participants) evaluated dupilumab. Disease-specific HRQL was measured with the SNOT-22 (a 22-item questionnaire, with a score range of 0 to 110; minimal clinically important difference (MCID) 8.9 points). At 24 weeks, dupilumab results in a large reduction (improvement) in the SNOT-22 score (mean difference (MD) -19.61, 95% confidence interval (CI) -22.54 to -16.69; 3 studies; 784 participants; high certainty). At between 16 and 52 weeks of follow-up, dupilumab probably results in a large reduction in disease severity, as measured by a 0- to 10-point visual analogue scale (VAS) (MD -3.00, 95% CI -3.47 to -2.53; 3 studies; 784 participants; moderate certainty). This is a global symptom score, including all aspects of chronic rhinosinusitis symptoms. At between 16 and 52 weeks of follow-up, dupilumab may result in a reduction in serious adverse events compared to placebo (5.9% versus 12.5%, risk ratio (RR) 0.47, 95% CI 0.29 to 0.76; 3 studies, 782 participants; low certainty). Anti-IL-5 mAb (mepolizumab) versus placebo/no treatment (all receiving intranasal steroids) Two studies (137 participants) evaluated mepolizumab. Disease-specific HRQL was measured with the SNOT-22. At 25 weeks, the SNOT-22 score may be reduced (improved) in participants receiving mepolizumab (MD -13.26 points, 95% CI -22.08 to -4.44; 1 study; 105 participants; low certainty; MCID 8.9). It is very uncertain whether there is a difference in disease severity at 25 weeks: on a 0- to 10-point VAS, disease severity was -2.03 lower in those receiving mepolizumab (95% CI -3.65 to -0.41; 1 study; 72 participants; very low certainty). It is very uncertain if there is a difference in the number of serious adverse events at between 25 and 40 weeks (1.4% versus 0%; RR 1.57, 95% CI 0.07 to 35.46; 2 studies; 135 participants, very low certainty). Anti-IgE mAb (omalizumab) versus placebo/no treatment (all receiving intranasal steroids) Five studies (329 participants) evaluated omalizumab. Disease-specific HRQL was measured with the SNOT-22. At 24 weeks omalizumab probably results in a large reduction in SNOT-22 score (MD -15.62, 95% CI -19.79 to -11.45; 2 studies; 265 participants; moderate certainty; MCID 8.9). We did not identify any evidence for overall disease severity. It is very uncertain whether omalizumab affects the number of serious adverse events, with follow-up between 20 and 26 weeks (0.8% versus 2.5%, RR 0.32, 95% CI 0.05 to 2.00; 5 studies; 329 participants; very low certainty).
AUTHORS' CONCLUSIONS
Almost all of the participants in the included studies had nasal polyps (99.8%) and all were using topical nasal steroids for their chronic rhinosinusitis symptoms. In these patients, dupilumab improves disease-specific HRQL compared to placebo. It probably also results in a reduction in disease severity, and may result in a reduction in the number of serious adverse events. Mepolizumab may improve disease-specific HRQL. It is very uncertain if there is a difference in disease severity or the number of serious adverse events. Omalizumab probably improves disease-specific HRQL compared to placebo. It is very uncertain if there is a difference in the number of serious adverse events. There was no evidence regarding the effect of omalizumab on disease severity (using global scores that address all symptoms of chronic rhinosinusitis).
Topics: Adult; Anti-Allergic Agents; Antibodies, Monoclonal, Humanized; Bias; Biological Products; Chronic Disease; Humans; Nasal Obstruction; Nasal Polyps; Omalizumab; Placebos; Quality of Life; Randomized Controlled Trials as Topic; Rhinitis; Sinusitis; Treatment Outcome
PubMed: 33710614
DOI: 10.1002/14651858.CD013513.pub3 -
Chemical Senses Jan 2022Little attention has been paid to olfactory changes during pregnancy with contemporary studies limited in number and sample size. We examined whether pregnancy is... (Meta-Analysis)
Meta-Analysis
Little attention has been paid to olfactory changes during pregnancy with contemporary studies limited in number and sample size. We examined whether pregnancy is associated with differences in olfactory performance and if there were any specific gestational ages at which these differences occur through a comprehensive systematic review and meta-analysis of the current literature. An initial electronic database search identified 234 citations, which were screened at the abstract level. Twenty-three citations were germane for full-text review, and 13 met criteria for inclusion. Our review assessed 5 olfactory measures of interest: odor identification (n = 11 articles), threshold (n = 8), discrimination (n = 5), hedonics (n = 6), and intensity (n = 5). Nine of these 13 studies contained sufficient data for meta-analysis, and these studies included a total of 523 pregnant women and 365 non-pregnant controls. Despite previous subjective and objective reports of odor intolerances and odor hypersensitivity, we did not find any significant differences between pregnant and non-pregnant women in odor discrimination, thresholds, or hedonics. However, meta-analysis of 506 cases and 333 controls showed worse odor identification in pregnant women compared to controls in a random-effects model. Thus, we demonstrate worse performance at odor identification during pregnancy. In this review, we discuss the current evidence (and lack thereof) regarding olfaction in pregnancy as well as highlight current knowledge gaps in this field.
Topics: Pregnancy; Humans; Female; Smell; Odorants; Olfaction Disorders
PubMed: 36469055
DOI: 10.1093/chemse/bjac035 -
European Review For Medical and... Sep 2021We aimed this systematic review to analyze and review the currently available published literature related to long COVID, understanding its pattern, and predicting the...
We aimed this systematic review to analyze and review the currently available published literature related to long COVID, understanding its pattern, and predicting the long-term effects on survivors. We thoroughly searched the databases for relevant articles till May 2021. The research articles that met our inclusion and exclusion criteria were assessed and reviewed by two independent researchers. After preliminary screening of the identified articles through title and abstract, 249 were selected. Consequently, 167 full-text articles were assessed and reviewed based on our inclusion criteria and thus 20 articles were regarded as eligible and analyzed in the present analysis. All the studies included adult population aged between 18 and above 60 years. The median length of hospital stay of the COVID-19 patients during the acute infection phase ranged from 8 days to 17 days. The most common prevalent long-term symptoms in COVID-19 patients included persistent fatigue and dyspnea in almost all of the studies. Other reported common symptoms included: shortness of breath, cough, joint pain, chest pain or tightness, headache, loss of smell/taste, sore throat, diarrhea, loss of memory, depression, anxiety. Associated cardiovascular events included arrhythmias, palpitations and hypotension, increased HR, venous thromboembolic diseases, myocarditis, and acute/decompensated heart failure as well. Among neurological manifestations headache, peripheral neuropathy symptoms, memory issues, concentration, and sleep disorders were most commonly observed with varying frequencies. Mental health issues affecting mental abilities, mood fluctuations namely anxiety and depression, and sleep disorders were commonly seen. Further, diarrhea, vomiting, digestive disorders, and Loss of appetite or weight loss are common gastrointestinal manifestations. Therefore, appropriate clinical evaluation is required in long COVID cases which in turn may help us to identify the risk factors, etiology, and to my help, we treat them early with appropriate management strategies.
Topics: COVID-19; Humans; SARS-CoV-2; Post-Acute COVID-19 Syndrome
PubMed: 34533807
DOI: 10.26355/eurrev_202109_26669 -
OTO Open 2020Loss of smell and taste are considered potential discriminatory symptoms indicating triaging for coronavirus disease 2019 (COVID-19) and early case identification.... (Review)
Review
OBJECTIVE
Loss of smell and taste are considered potential discriminatory symptoms indicating triaging for coronavirus disease 2019 (COVID-19) and early case identification. However, the estimated prevalence essential to guide public health policy varies in published literature. This meta-analysis aimed to estimate prevalence of smell and taste loss among COVID-19 patients.
DATA SOURCES
We conducted systematic searches of PubMed, Embase, Web of Science, and Google Scholar databases for studies published on the prevalence of smell and taste loss in COVID-19 patients.
REVIEW METHODS
Two authors extracted data on study characteristics and the prevalence of smell and taste loss. Random-effects modeling was used to estimate pooled prevalence. Subgroup analysis and meta-regression were conducted to explore potential heterogeneity sources. This study used PRISMA and MOOSE guidelines.
RESULTS
Twenty-seven of 32 studies reported a prevalence of loss of smell, taste, or both from a combined sample of 20,451 COVID-19 patients. The estimated global pooled prevalence of loss of smell among 19,424 COVID-19 patients from 27 studies was 48.47% (95% CI, 33.78%-63.29%). Loss of taste was reported in 20 studies and 8001 patients with an estimated pooled prevalence of 41.47% (95% CI, 3.13%-31.03%), while 13 studies that reported combined loss of smell and taste in 5977 COVID-19 patients indicated a pooled prevalence of 35.04% (95% CI, 22.03%-49.26%).
CONCLUSIONS
The prevalence of smell and taste loss among COVID-19 patients was high globally, and regional differences supported the relevance of these symptoms as important markers. Health workers must consider them as suspicion indices for empirical diagnosis of severe acute respiratory syndrome coronavirus 2 infection.
PubMed: 32964177
DOI: 10.1177/2473974X20957975 -
International Journal of Infectious... Apr 2022Chemosensory disorders associated with COVID-19 have been widely discussed during the pandemic. We performed a meta-analysis to assess the risk factors for olfactory and... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Chemosensory disorders associated with COVID-19 have been widely discussed during the pandemic. We performed a meta-analysis to assess the risk factors for olfactory and gustatory dysfunction in patients with COVID-19.
METHODS
Three databases (PubMed, Embase, and Cochrane Library) were searched for studies published between December 1, 2019, and August 31, 2021. We selected random-effects model or fixed-effects model to pool data based on heterogeneity. The results were reported as odds ratios (ORs) or standardized mean differences (SMDs) and the corresponding 95% confidence intervals (CIs). Heterogeneity was reported as I.
RESULTS
Twenty-six studies with a total of 13,813 patients were included. The pooled data indicated that sex (OR 1.47; 95% CI 0.93-2.31), age (SMD -5.80; 95% CI -13.35 to 1.75), smoking (OR 2.04; 95% CI 0.72-5.79), and comorbidity (OR 1.21; 95% CI 0.58-2.53) of patients with COVID-19 had no effect on gustatory dysfunction. Olfactory dysfunction was more likely to occur in older patients with COVID-19 (SMD, -5.22; 95% CI, -8.28 to -2.16). Patients with COVID-19 with nasal congestion (OR 3.41; 95% CI 2.30-5.06) and rhinorrhea (OR 2.35; 95% CI 1.60-3.45) were more prone to olfactory dysfunction.
CONCLUSION
These findings emphasize that older patients with COVID-19 are more likely to experience olfactory dysfunction. Symptoms of nasal congestion and rhinorrhea may affect the recognition of olfactory dysfunction.
Topics: Aged; COVID-19; Humans; Olfaction Disorders; Prevalence; SARS-CoV-2; Taste Disorders
PubMed: 35134561
DOI: 10.1016/j.ijid.2022.02.004